Once roasted and ground, coffee is known to be extremely sensitive to the conditions of the environment in which it is located, in the sense that they can considerably influence the result of the beverage obtained in terms of taste and quality.
One of the conditions which mostly influence the beverage quality is the temperature of the ground coffee powder at the moment in which the hot water flow passes through it on preparation.
The temperature of the ground coffee powder can firstly vary with varying temperature of the environment in which the coffee grinder operates.
Of even greater influence however is the heating effect produced by the grinding itself. In fact, such machines generate on the coffee beans a considerable friction causing the powder to undergo heating. Sometimes the machine action itself can cause overheating of the coffee powder.
Examples of known espresso coffee dispensing systems can be seen in WO 2010/085850, DE 20 2009 009496 and EP 1 584 273.
The effect of temperature on the coffee powder is reflected in the quality of the beverage obtained.
In this respect, it is found that the higher the coffee powder temperature, the more the extraction time (i.e. the time in which a predetermined hot water quantity passes through the coffee powder) decreases. In other words, extraction becomes quicker.
This determines less effective extraction of the coffee aromatic components. Moreover, the cream obtained is more unstable, deteriorating rapidly.
This causes a further aroma loss from the beverage, as the cream helps to maintain the aromatic substances within the beverage.